Invasive fungal infections, such as cryptococcosis, candidiasis and aspergillosis, have dramatically emerged in the last two decades and are associated with very poor prognosis. Although significant progress has been made to improve molecular and genetic tools to study their development and progression, studies to provide better tools for an early diagnosis are urgently needed. Ultimately, these tools will significantly help in the management of invasive mycoses. In recent years, our laboratory has centered on dissecting molecular mechanisms of fungal pathogenesis, focusing on the study of the role of bioactive lipids in this process both at a mechanistic and at a translational level. We discovered in our mouse model that a fungal lipid molecule called glucosylceramide (GlcCer) is an essential regulator of the invasiveness of Cryptococcus neoformans (Cn), an environmental fungus that, once inhaled, causes cryptococcosis, an invasive fungal disease which can lead to life-threatening meningo- encephalitis in susceptible human subjects. In particular, we found that, in contrast to wild-type cells, Cn cells that do not produce GlcCer are contained within lung granulomas and cannot disseminate to the central nervous system (CNS). As a result, the host remains healthy without any clinical sign(s) of meningo- encephalitis. Interestingly, cryptococcal GlcCer produced by wild-type cells elicits a host antibody response, and IgM against GlcCer can be detected in mouse sera prior to the dissemination of wild-type Cn cells from the lung to the bloodstream and prior to the development of the meningo-encephalitis. Based on these observations, we hypothesize that GlcCer is required for Cn to leave the lung and infect the brain and that the detection of serum IgM against fungal GlcCer can be used as an early diagnostic method of cryptococcosis. Thus, to address this hypothesis we propose the following aims: 1) to determine the role of GlcCer in the in the development of cryptococcosis;and 2) to determine the value of anti-GlcCer antibody for the prediction of disseminated cryptococcosis in immunocompromised subjects. These studies will be performed using an ELISA test that we have developed. Importantly, because GlcCer is also produced by Candida and Aspergillus spp., the results from these studies not only could provide a new method for the early diagnosis of cryptococcosis but could also prompt new means for the early diagnosis of candidiasis and aspergillosis. PUBLIC HEALTH RELEVANCE Invasive fungal infections, such as cryptococcosis, candidiasis and aspergillosis, have dramatically emerged in immunocompromised subjects. This project aims to develop a new diagnostic method that would predict the invasiveness of fungal infections so that appropriate treatment strategies can be implemented. This will have a dramatic effect on human health as invasive fungal diseases have very poor prognosis.